Csonka was born on Christmas Day, 1946. At nine pounds and 13 ounces, he was apparently a lot to handle right from the start. He grew into a 6'3", 237 lb. All-American fullback for the Syracuse Orangemen. Miami selected him in the first round of the 1968 NFL Entry draft with the eighth overall pick.
As a rookie, Csonka started each of the 11 games in which he appeared. He scored a team high (and an AFL fourth best) six rushing touchdowns for the 5-8-1 Dolphins, finishing second to fellow rookie Jim Kiick with 138 rushes for 540 yards. He also caught 11 passes for 118 yards and another score.
In 1969, Csonka again started 11 games for Miami, as the team finished at the bottom of the AFL with a 3-10-1 record. He again ranked second on the team with 131 carries for 566 yards and two scores. He also caught a career high 21 passes for 183 yards and another touchdown. In a week nine 17-16 victory over the Boston Patriots, he rushed 16 times for 121 yards and a touchdown, his first 100+ yard effort.
1970 would see the AFL join the NFL under new head coach Don Shula. Csonka responded with his best season to date, starting every game and earning his first Pro Bowl invitation in the process. He ranked fifth in the NFL with a team best 874 rushing yards, 4.5 yards per carry, and 62.4 rushing yards per game on 193 carries, scoring six touchdowns. He also caught 11 passes for 94 yards. Miami's rushing attack led the AFC with 2,082 yards as the team made their first postseason with a 10-4 record. In a two game stretch near the end of the season, (both wins) Csonka strung together consecutive 100-yard games, gaining a total of 223 yards on 40 carries, scoring twice.
Csonka posted his first 1000-yard season in 1971, leading the team with an NFL third-best 1,051 rushing yards while leading the league with 5.4 yards per carry, starting every Dolphin game. He was selected as a first-team All-Pro for the first time, earning his second consecutive trip to the Pro Bowl. Csonka carried the ball 195 times and scored seven touchdowns, catching the ball 13 times for 113 yards and a touchdown. Miami's offense led the NFL with 2,429 rushing yards and with 5.0 yards per carry. The team won the AFC East with a 10-3-1 record, advancing to Super Bowl VI against the Dallas Cowboys. Csonka broke the 100-yard barrier on three occasions, his best performance in a week six 30-14 victory over the New York Jets, where he rushed 20 times for 137 yards and two touchdowns.
In Miami's legendary 1972 season, Csonka started every game, gaining a career high (and NFL fourth best) 1,117 yards on 213 carries and scoring six touchdowns and making his third consecutive Pro Bowl. He also caught five passes for 48 yards. The Dolphins offense led the NFL with 385 points scored and 5,036 yards gained. The rushing offense led the league by far with 613 rushes for 2,960 yards and 26 touchdowns. Csonka posted four 100-yard rushing performances during the regular season, capping the year with 15 carries for 112 yards in Miami's Super Bowl VII victory over the Washington Redskins, 14-7.
In 1973, Csonka again started all 14 games, gaining an NFL fifth best 1,003 yards on 219 carries and scoring five touchdowns. He was for the second time selected to the All-NFL First Team, also earning his fourth consecutive Pro Bowl invitation. He also caught seven passes for 22 yards. Miami's offense led the NFL with 5.3 yards average gain per play, finishing second in the AFC with 2,521 rushing yards. The team finished the season with an AFC East title earning 12-2 record, eventually winning their second consecutive Super Bowl, 24-7 over the Minnesota Vikings. Csonka gained over 100 yards three times during the regular season. In the AFC Championship, he gained 117 yards on 29 carries, scoring three touchdowns as the Dolphins eliminated the Oakland Raiders, 27-10. The next week, Csonka was named the Super Bowl VIII MVP as he gained 145 yards and scored twice on 33 carries.
1974 would see Csonka start each of the 12 games in which he appeared for the Dolphins. He earned his fifth consecutive trip to the Pro Bowl by leading Miami with 197 rushes for 749 and nine touchdowns. He also caught seven passes for 35 yards. Miami's rushing offense ranked fourth in the NFL with 2,191 yards on an NFL high 570 rushes. The Dolphins again won the AFC East, this time with an 11-3 record. Csonka rushed for over 100-yards three times, including a 24 rush, 114 yard performance in a 28-26 loss to the Oakland Raiders in the Conference Semifinal.
After the season, Csonka, along with teammates Jim Kiick and Paul Warfield, bolted for the upstart WFL franchise, the Memphis Southmen. The league failed in short order, and Csonka rejoined the NFL with the New York Giants for the 1976 season. Over three seasons, he gained 1,344 yards on 385 carries, scoring 11 touchdowns. He only broke the 100-yard barrier once while with the franchise.
In 1979 Csonka came back to the Dolphins for one final season. He started all 16 games, winning the NFL Comeback Player of the Year Award by leading the Dolphins with 220 rushes for 837 yards and a career high 12 touchdowns. He also caught 16 passes for 75 yards and a touchdown. He did not post a 100-yard rushing performance during his final year, but did score three touchdowns on two occasions, a week four, 31-16 victory over the Chicago Bears, and a week 14, 39-24 victory over the New England Patriots.
Csonka tops Miami's all-time leader board with 6,737 rushing yards and with 53 rushing touchdowns. He was selected to the Pro Football Hall of Fame with the Class of 1987, along with teammate Jim Langer. His number 39 was retired by the Dolphins in 2002.
Since retirement, Csonka has hosted several hunting and fishing shows for the Outdoor Life Network, and currently resides in Anchorage, Alaska.